The present invention relates to the purification of liquids such as water; and, more particularly, to improved purification devices wherein liquid flow is initiated by gravity through a filter containing an adsorption-bactericidal material, and the flow continues without using any additional sources of external pressure. Use of the improved device causes a flow pattern of liquid passing therethrough of such nature that the adsorption and bactericidal purification is enhanced and the quality of the purified liquid is thereby significantly higher than heretofore available.
As medical and ecological information has increasingly shown that water pollution leads to illnesses, and as pollution of natural water resources, caused at least in part by population growth, has also increased, it has become obvious that it is necessary to use purified drinking water. The public clearly demands that the quality of its drinking water must be improved to ever greater levels. The need to filter water at home; and, particularly, the desirability of using point-of-use water filtration systems has become evident.
Typical point-of-use water filtration systems comprise a vessel that contains the liquid to be filtered. A cartridge filter is secured at the bottom of the vessel. Water flows into the top of the filter, passes downward by gravity through the filter cartridge where the water is purified. Purified liquid passes out through the bottom of the filter cartridge and is collected in another vessel which is located below the first vessel. Most commonly, the filter material comprises granular activated carbon, which removes chlorine, organics and other impurities.
In order to provide effective filtration employing such devices it is necessary, on one hand, to provide liquid flow through the filter with a minimum resistance, and, on the other hand, to provide required liquid residence time which is necessary for the adsorption of the dissolved impurities from liquid. Currently used filters employing granular adsorbents do not completely provide adequate resistance against the liquid flow.
To retain the adsorbent particles inside a filter cartridge, an additional filter element with small pores is often placed at the exit end of the prior art filter cartridge. This filter element often becomes plugged by small dust particles that move downward together with the liquid as it passes through the granular adsorbent. Plugging of the end filter significantly reduces the filtration capacity of the filter. Another problem is the visual control of the work of the filter, and controlling the quantity of the liquid that is being filtered.
Shown in U.S. Pat. No. 5,536,394 is a device for drinking water purification, comprising a housing, which has at least one opening for passing liquid into a chamber which is formed by the internal volume of the housing and a water treating cartridge, which includes a mechanism indicating the length of service of the water treating cartridge. This mechanism comprises a float that makes turns as a result of a cyclical use of the water filter. Said mechanism indicates the end of the service life of the water treating mechanism. After the float makes a specified number of turns, it stops in a position where it is visible through an opening in the housing.
Prior art filters are subject to another problem. For practical purposes, known constructions provide for liquid flow downwardly under gravitational forces with the liquid entering the filter element through the top part, and the purified liquid removed from the bottom part of the filter element. In such configurations, gas and air bubbles form inside the filtration material. These bubbles block pores, making liquid flow through the filter more difficult. Sometimes, they can even block liquid flow through the filter completely. To solve this problem there are designed special gas-catching constructions in the filter. This makes the filters more complicated and expensive, and limits the possible scope of their use.
Another significant drawback of known filter designs, wherein filtration takes place by the downward flow caused by gravity, is a complete drying out of the filter after the end of the filtration process. This limits the selection of ion-exchange materials that can be employed as filtration and adsorption agents, because many can not stand up to the periodically changing drying and wetting conditions, and they cease to perform properly.
One prior art filtration device similar in some respects to that of the present invention is a water filtration device that is described in U.S. Pat. No. 4,969,996. It comprises a conical container for the liquid to be purified, a separate container for the purified liquid, which is snugly fit to the conical container, and a removable filtration element that has nearly cylindrical walls, a top part and a bottom part. The filtration element contains a purification agent of the granular type therein. In order to avoid gases and/or air that are collected from becoming a barrier to the flow of liquid through the bottom part, a gas collecting fixture is provided in the form of a gas collecting cavity and gas collecting channels along the side walls of the filter element. Construction of such a filter element is difficult. Furthermore, filtration takes place by the xe2x80x9cchanneling flow,xe2x80x9d wherein liquid is being filtered through the filtration material non-uniformly along the separate channels. As a result some of the liquid that is being filtered moves through the filter faster than required for effective purification.
Known filters wherein filtration takes place in the downward direction either require using pressure from the water tap line (which limits where the filter can be used), or require hydrostatic pressure of an additional column of liquid (which does not purify the entire liquid volume, due to loss of pressure from the additional column of liquid), or require using additional complicated fixtures and constructions for effecting filtration.
There are technical problems, of the nature of those set forth above, that have not been solved until the present invention and which restrain the potential growth of use of liquid purification devices. Attempts to solve these problems in the known designs have led either to more complicated and expensive constructions or to the incomplete purification of at least a part of the liquid that is being filtered.
The objects of this invention are to improve the quality of liquid purification by providing a device which prevents premature plugging up of the pores of the filtration material, achieves better quality filtration and adsorption of the impurities, eliminates channeling, removes air and gasses, and maintains the filter element fully filled with liquid.
A primary object of this invention is to improve the quality of liquid filtration by providing a method that entails upward flow of the liquid during filtration.
Still another object is to enable quality liquid purification by providing liquid filtration by liquid flow in the upward direction using natural gravitational forces while, at the same time, the construction of the filter is simplified and made less expensive. Also, filtration in the filter is organized in such a way that while liquid is flowing by itself in the upward direction, the level where the purified liquid is being removed from the filter can be higher than the level at which liquid is being introduced into the filtration cartridge.
An additional object of this invention is to provide an automatic air and/or gas removal from the filtration material to improve purification and to have the filter cartridge fully filled with liquid after the end of the filtration, thereby prolonging usage of the filtration material.
A further object of the invention is to create a filter and filter cartridge which make it possible to have the filter design significantly simpler, cheaper and easier to manufacture, and which improves quality of filtration and lengthens the usage of the filtration material while, at the same time, reduces the filter resistance and improves purification ability as compared to the known filters for liquid filtration.
The objects of the invention are achieved by providing a device for liquid purification comprising in combination a container for liquid and a filter cartridge positioned inside the container and at its bottom. The filter cartridge comprises a housing with a filtration chamber therein and a sealed cavity in the upper portion thereof. A liquid inlet is at the bottom of the housing to permit liquid to flow from the container into the filter cartridge, upwardly through the filtration chamber, into a sealed cavity, and downwardly out of the filter cartridge through a fluid conduit of restricted cross sectional area the exit end of which is elongated to extend below the liquid inlet in the bottom of the filter cartridge. A vacuum is created in the sealed cavity which causes a siphon effect that draws additional liquid through the filter cartridge.